1. Field of the Invention (Technical Field)
The present invention relates to methods and apparatuses for explosively breaching targets including but not limited to masonry walls, stucco walls, wood and metal doors, and EOD applications, using a limited amount of explosive material and producing low-density, high-air-drag-resistant debris from the exploding charge.
2. Description of Related Art
Note that where the following discussion refers to a number of publications by author(s) and year of publication, that due to recent publication dates certain publications are not to be considered as prior art vis-a-vis the present invention. Discussion of such publications herein is given for more complete background and is not to be construed as an admission that such publications are prior art for patentability determination purposes.
Various techniques currently use explosives for creating openings through walls as well as breaching doors and other entry-ways. Most entry teams use detonating cord and sheet explosive as the preferred explosive material, due to their availability and the ease of charge fabrication from these components. Detonating cord is used as a main explosive charge because it offers a means of modulation of energy by employing different size core loads as well as using multiple strands of detonating cords. Sheet explosive provides the same select ability of energy modulation by varying the thickness and geometry of sheet explosive.
To optimize performance, charge design should incorporate many factors including shock pulse intensity required for defeating the target, shock pressure duration requirements, hardness of the target, the target failure mechanism, the target fracture toughness, target surface area available, tamping material efficiency, and volume constraints. In close quarter breaching (CQB) operations, commonly encountered targets range from pine wood doors to eight-inch thick reinforced concrete walls. For penetration and for severance of high-strength materials such as steel, high impact pressures greater than two million psi are generally required whereas for wood targets pressures for target defeat are generally less than 10,000 psi. Typically, steel targets need high-intensity short-pulse shocks for defeat whereas masonry targets require longer-pulse lower-intensity shocks for defeat. Conventional rectangular shaped contact charges to sever steel targets require a width to thickness ratio between 2 to 1 and 4 to 1. Conventional rectangular shaped contact charges to sever masonry targets require a width to thickness ratio between 8:1 and 16:1.
To enhance the effect of explosives, some currently-used field fabricated charges as well as commercially manufactured charges use a tamper mass to confine the explosive charge. Tamper mass is an inertial mass of material adjacent to or in direct contact with a high explosive charge. Its purpose is to prolong and sustain the pressure of the explosive charge. Tamper mass retards the release waves created by a high explosive. Release waves are shock waves reflecting at the explosive's boundaries due to shock impedance mismatch that relieve pressure in the detonating explosive. Due to the higher density and different sound wave propagation properties of tamper mass (i.e. water, plastics, metals etc) versus air, there is less reflection (the creation of release waves) at the tamper/explosive boundary, thus sustaining and prolonging the explosives' energy. The inertial tamper mass also confines the gas in the early stages (˜tens of microseconds) of gas expansion produced from the detonating high explosives, thus adding impulse to the event, where impulse is the time integral of pressure over a finite time interval, defined as the calculus integral of ∫Pdt.
The effective range of tamper mass when associated with high explosive charges is complex. Depending on the work function, i.e. explosively driving a metal plate or projectile or blowing stumps, the effectiveness can vary up to a factor of fifty. Tamper mass's effective range for CQB operations can increase the explosive's efficiency between 25% and 300%.
Depending on the tamper mass, tamping can increase the impulse of the explosive charge significantly. The most often used tamper mass is water. Water has the unique ability to provide adequate tamping and dissipates into small droplets at a relatively short distance from the exploding charge. The main disadvantages of using water are its relatively high freezing temperature, the possibility of leaking charges, and creating a slippery environment for operators. Other tamping materials, such as high density polyethylene strips as well as conveyor belt rubber strips, have been used in explosive entry systems to increase charge efficiency. Since relatively small quantities of explosive are used in explosive entry these materials most often remain intact after detonation and create dangerous fragments that can be lethal to the CQB operators as well as damage to surrounding property. Backofen, Petrousky, Butz cite the use of a frangible mixture of dental plaster and metal powder cast into a desired shape to enhance the performance of explosive charges. Backofen et al. also cites that projectiles can be made from this material that can withstand impacts and that can transfer energy for target penetration. A projectile comprised of this material (typically called “AVON”) fired from a shotgun can penetrate a ¾″ wood plyboard barrier before disintegrating. For EOD operations the disintegrating tamper mass is suitable since almost all personnel are remotely positioned during the dismantlement of bombs.
Due to small quantities of explosives used in close quarter explosive entry operations, the frangible tamper mass as described by Backofen, Petrousky, Butz, does not readily disintegrate into very fine particles. As the material adjacent to the explosive charge radius increases, the shock pressure and tensile waves attenuate as the inverse square of the distance from the detonating explosive. Explosive charges enveloped in the material used for explosive entry upon detonation can produce lethal fragments in close proximity (5-15 ft.) to Special Weapons and Tactics (SWAT) operators.
In the art of explosive entry systems used by SWAT and CQB teams, most tamped explosive systems produce undesired fragmentation that can travel long distances from the explosive charge. Typical commercial explosive entry systems that are injection molded from various plastics that house water have relatively thick plastic walls. When detonated these charges produce dangerous fragments that can travel in excess of fifty yards. The most desired explosive charges used for explosive entry employ the minimum amount of explosive thus reducing air blast and other unwanted damage to the surroundings. Additionally, other desired features are charges that produce little or no fragmentation, are lightweight, and are easy to deploy.
In the art of explosive entry systems currently used by SWAT and CQB teams, most explosive systems consist of detonating cords taped to the door that is to be breached. As many as four strands of detonating cords may be required to breach typical doors. Currently, many SWAT and CQB teams use products that result in excessive explosive force, resulting in increased liability.
For those skilled in the art of explosive entry for close quarter breaching, the ideal charge is one that delivers the optimum energy pulse to effectively breach the target, use the minimum amount of explosive to control air blast, and charges that produce the minimum amount of fragmentation on both sides of the target when the target is attacked. The present invention preferably provides an explosive system that optimizes the explosive impulse delivered to the target thus preferably minimizing by greater than 50% the quantity of explosives required to successfully breach a given target.
Those skilled in the art of explosive entry are familiar with the cutting action of linear shaped charges. These charges are generally comprised of powdered explosive housed in a chevron shaped metallic sheath. The purpose of the metallic sheath is to provide confinement and produce a high velocity metallic jet. This metallic jet is capable of cutting or penetrating hardened targets such as steel barriers. The disadvantage of these metallic sheathed linear shaped explosive charges used for close quarter explosive breaching is that they produce high speed, dangerous fragments. Some charges contain a sheath material composed primary of lead and produce dangerous lead vapors.
The present invention preferably provides explosives used by SWAT and military COB teams to gain entry through barriers such as doors, walls, roofs, and floors. Firefighters utilize these systems to vent buildings. Additionally, rescue personnel utilize these systems to create portals or holes through barriers to assist in rescuing trapped personnel. The present invention preferably provides the maximum destructive force against structures using the least amount of explosives.
The present invention preferably provides a sustained focused pressure which creates a cutting action into the target. The present invention preferably provides a means to cut reinforcing members such as reinforcing wire used in the construction of stucco type wall construction, the penetration of multiple layers of construction materials commonly used in roof construction, and other similar targets that require a cutting action to achieve target defeat. The present invention preferably provides a culling action or deep penetration without the use of a dangerous metallic jet or penetrating projectile. The present invention preferably customizes the communicative explosive energy profile providing optimum impulse to the desired target. This customization is achieved through the combination of a variety of factors including the engineered selection of: shock lensing material and geometry, shock spreader material and geometry, explosive geometry, explosive quantity, explosive type, explosive inertial tamping material, tamping material quantity and type. Each factor is use to tailor the charge for use on a variety of targets. The shock spreader material can be various shapes and thicknesses to optimize the shock pulse for specific targets. If there is intelligence that indicates a structure to be breached is of a specific nature, charge selection based upon the listed factors may be employed to provide maximum efficiency. A kit comprising different thicknesses of spreader bars can be used by personnel in the field.
A variety of connectors including but not limited to adhesives can be used to attach the present invention securely to a structure. Adhesives can be sheet adhesives and can be precut or cut to the needed size and configuration.
The present invention optimizes breaching performance, minimizes fragmentation, and maximizes power in a controlled, almost surgical fashion. The present invention comprises a charge that is for one time use only.
Metal liners and hollow portions are absent from the present invention.